Method and system for operating a gas burner for industrial use with at least two fuel gases

Abstract

The invention relates to a method for operating at least one gas burner for industrial use with at least two fuel gases, which are fed by means of a first fuel gas line (1a) and at least one further fuel gas line (1b, 2c) to a mixing unit (3) for generating a fuel gas mixture, wherein the proportions of the fuel gases in the fuel gas mixture are predetermined, with at least the following method steps: - determining the fuel gas with the largest proportion as the guide gas and the at least one further fuel gas as the follower gas by means of a control / regulation unit (6), - regulating the pressure of the guide gas, wherein the setpoint value (p2G) of the pressure of the guide gas is predetermined as a function of the desired heating output, - regulating the pressure of the follower gas, wherein the setpoint value of the pressure of the follower gas is higher than the setpoint value (p2G) of the pressure of the guide gas by a predetermined pressure difference, - guiding the follower gas to a control valve (11,11') and controlling the volume flow, wherein the setpoint value of the volume flow of the follow-up gas is determined as a function of the proportion of the follow-up gas in the fuel gas mixture, - supplying combustion air to the gas burner (5) by means of a fan (19), wherein the volume flow of the combustion air is controlled.

Description

[0001] The invention relates to a method and a system for operating at least one gas burner for industrial use with at least two fuel gases, which are supplied via a first fuel gas line and at least one further fuel gas line to a mixing unit for generating a fuel gas mixture, which is then provided to the gas burner. The proportions of the fuel gases in the fuel gas mixture are predetermined or determined. Furthermore, the invention relates to a corresponding system.

[0002] In industry, process heat is required for various manufacturing processes. An important application for gas burners to generate process heat is the heat treatment of metals, especially steel products in industrial furnaces. The steel products are heated in a controlled manner, or heated and then cooled to change the material properties. Common heat treatments include annealing, tempering, and hardening. Because the temperatures involved in heat treatment are generally relatively high, heat treatment processes are energy-intensive.

[0003] Gas burners for industrial use are currently primarily powered by natural gas. This is due to the relatively low cost of natural gas in the past. However, the procurement costs for natural gas are currently at a high level. Furthermore, the use of natural gas contributes to an increase in greenhouse gas emissions in the atmosphere and leads to air pollution.

[0004] In addition to the increased use of electric heat sources for industrial processes, alternative fuel gases are becoming increasingly important instead of natural gas. These can include fuel gas from biogenic sources such as biogas, biomethane, or hydrogen.

[0005] Hydrogen, in particular, is a suitable partial or full replacement for natural gas because it enables carbon-free combustion with no impact on greenhouse gas emissions. From an ecological perspective, hydrogen is an ideal fuel.

[0006] The electrolysis of water represents a virtually inexhaustible energy source, but requires the use of electrical energy, which is primarily to be generated from renewable sources such as wind and solar energy. However, the production and supply of hydrogen fluctuate depending on weather conditions. Furthermore, the development of a hydrogen distribution infrastructure is currently still in its early stages, meaning that hydrogen will only be available in highly fluctuating quantities as a fuel for industrial applications for a transitional period.

[0007] Hydrogen can be added to natural gas in existing natural gas networks as an additional gas. A technical standard currently limits the feed-in quantity to 10 vol.% because hydrogen differs from natural gas in its physical and chemical properties.

[0008] From an industrial perspective, there is interest in replacing natural gas with at least one other fuel gas, particularly hydrogen, for generating process heat, with the greatest possible flexibility in terms of time. This requires that at least one gas burner can be operated simultaneously with at least two different fuel gases, usually with different calorific values. Furthermore, the aim is to ensure that the proportions of the fuel gases in the fuel gas mixture can be varied as required.

[0009] In addition, for industrial heating purposes, the heat output must be constant. It must be ensured that the heat output remains constant even when the proportions of the fuel gases in the fuel gas mixture change.

[0010] Fluctuations in the pressure of the fuel gas mixture present at the gas burner can lead to incomplete combustion or misignition of the gas burner.

[0011] When operating one or more gas burners at one power level, with individual gas burners or burner groups being switched on or off, the required total flow can change very quickly, leading to difficulties in control.

[0012] Against this background, the invention is based on the object of creating a simple method for operating at least one gas burner for industrial purposes with at least two fuel gases, which avoids the disadvantages described and which meets the requirements described above, in particular that the heating output remains constant when the proportions of the fuel gases in the fuel gas mixture change.

[0013] Another aspect of the task is that the proportions of the fuel gases in the fuel gas mixture can be changed as desired.

[0014] The task also consists in providing an appropriate system.

[0015] This problem is solved by the features of the independent claims. Advantageous further developments arise from the dependent claims.

[0016] According to the invention, the method for operating at least one gas burner for industrial use with at least two fuel gases comprises the following steps: The fuel gases are fed via a first fuel gas line and at least one further fuel gas line to a mixing unit for generating a fuel gas mixture, which is then provided to the gas burner. The proportions of the fuel gases in the fuel gas mixture are predetermined. Preferably, the volumetric proportions of the fuel gases in the fuel gas mixture are predetermined.

[0017] By means of a control and regulation unit, the fuel gas with the largest proportion is determined or specified as the lead gas and at least one other fuel gas is determined or specified as the follower gas.

[0018] The pressure of the guide gas is regulated by means of a pressure control unit, whereby the setpoint of the pressure of the guide gas is specified by means of the control / regulation unit depending on the desired heating output.

[0019] The pressure of the follower gas is controlled by a pressure control unit, whereby the setpoint of the pressure of the follower gas is higher than the setpoint of the pressure of the guide gas by a predetermined pressure difference.

[0020] The follow-up gas is fed to a control valve and the volume flow of the follow-up gas is regulated, whereby the setpoint of the volume flow of the follow-up gas is determined depending on the volume fraction of the follow-up gas in the fuel gas mixture.

[0021] Combustion air is supplied to the gas burner by means of a fan, whereby the volume flow of the combustion air is regulated and whereby the setpoint value of the volume flow is determined as a function of a predetermined combustion air ratio, ie the air ratio λ (lambda) and the predetermined proportions of the combustion gases in the combustion gas mixture.

[0022] The first fuel gas and at least one additional fuel gas are fed separately and simultaneously to the mixing unit to generate a fuel gas mixture. The proportions of the fuel gases in the fuel gas mixture are specified. Thus, a fuel gas mixture with a specified mixing ratio is generated from the first fuel gas and the additional fuel gas in the mixing unit.

[0023] The fuel gas mixture is supplied or made available to the gas burner when it is switched on or during phases in which the gas burner is switched on.

[0024] The first fuel gas may be a gaseous hydrocarbon or a mixture of gaseous hydrocarbons, in particular

[0025] Natural gas. The at least one additional fuel gas can be, for example, another gaseous hydrocarbon such as propane, biomethane, biomethane, or, in particular, hydrogen. The additional fuel gas can also be a mixture of different fuel gases.

[0026] The pressure of the guide gas is regulated in such a way that the gas burner provides the heating output required in the process.

[0027] The pressure of the follower gas is also regulated, with the setpoint pressure of the follower gas being raised by a specified pressure difference compared to the setpoint pressure of the lead gas. This minimizes the effect of the follower gas pressure downstream of the pressure regulator on the volume flow control or flow control of the follower gas.

[0028] The volumetric flow of the follower gas is controlled so that the volumetric mixing ratio remains constant. The volumetric mixing ratio of the fuel gases is continuously maintained constant across the entire power range.

[0029] The fuel gas mixture from the mixing unit is combined with the combustion air required for combustion in the combustion chamber or combustion space of the gas burner.

[0030] A further development is characterized in that the guide gas downstream of the pressure control unit is conducted to the mixing unit and the follower gas downstream of the pressure control unit is conducted to the control valve by means of a first lockable connecting line and at least one further lockable connecting line which connect the first fuel gas line and the further fuel gas line to one another, wherein the fuel gas lines are designed to be lockable.

[0031] The connecting lines are connected to the first fuel gas line and the second fuel gas line and establish a connection between the fuel gas lines. Through the connecting lines, the guide gas can be routed downstream of the pressure control unit to the mixing unit, and the follow-up gas can be routed downstream of the pressure control unit to the control valve.

[0032] Preferably, at least one controllable shut-off valve is arranged in each of the first fuel gas line and the further fuel gas line, preferably between the connection points at which the first connecting line and the further connecting line are connected to the first and the further fuel gas line.

[0033] The flow paths of the guide gas and follower gas can be freely selected using open and closed shut-off valves. This allows the mixing ratio of the fuel gases in the fuel gas mixture to be completely variable.

[0034] According to the invention, the supply of the fuel gases to the mixing unit is interrupted if the volume flow of at least one fuel gas is below a predetermined minimum value or above a predetermined maximum value.

[0035] An essential development of the method according to the invention is that the pressure control unit has a mechanical pressure control device which has a membrane which divides a chamber into a first and a second space and that the first space has a setpoint spring which acts on the membrane.

[0036] According to the invention, a zero point shift of the force of the setpoint spring is effected by introducing a non-flammable gas, preferably nitrogen, into the first space through an opening in the first space of the chamber of the pressure regulator.

[0037] When controlling the pressure of the follower gas, the predetermined pressure difference between the setpoint value of the pressure of the guide gas and the setpoint value of the pressure of the follower gas is preferably between 25 mbar and 500 mbar.

[0038] To control the volume flow of the follower gas, the volume flows of the guide gas and the follower gas are advantageously measured with at least one flow meter each and the measured values ​​are fed to a ratio control unit for generating a control signal for the control valve in order to keep a predetermined volumetric mixing ratio constant.

[0039] For safety reasons, it is advantageous to perform two volume flow measurements per fuel gas. This could be achieved using a flow meter, e.g., an orifice plate with two taps, or even two flow meters per fuel gas.

[0040] According to the invention, the speed of the fan is controlled or a control flap is used to regulate the volume flow of the combustion air.

[0041] The method according to the invention has the advantage that industrial heating systems with at least one gas burner can be easily operated simultaneously with at least two different fuel gases, usually with different calorific values, whereby the proportions of the fuel gases in the fuel gas mixture can be varied as desired. This makes it possible to replace climate-damaging fuel gases, in particular natural gas, with at least one other fuel gas, in particular hydrogen, for generating process heat with the greatest possible flexibility.

[0042] In terms of device technology, the problem is solved as follows: System for operating at least one gas burner for industrial use with at least two fuel gases, with a first fuel gas line and at least one further fuel gas line for supplying the fuel gases to a mixing unit for producing a fuel gas mixture, which is provided to the gas burner by means of a fuel gas mixture line, wherein the proportions of the fuel gases in the fuel gas mixture are predetermined, at least comprising: a control / regulation unit configured to determine, from the predetermined proportions of fuel gas in the fuel gas mixture, the fuel gas with the largest proportion in the fuel gas mixture as the lead gas and the additional fuel gas as the follower gas; a pressure control unit in each fuel gas line, wherein each pressure control unit can be used selectively to regulate the pressure of the lead gas or to regulate the at least one follower gas; the control / regulation unit configured to specify a setpoint for the pressure of the lead gas depending on the desired heating output and to specify a setpoint for the pressure of the follower gas that is higher than the setpoint for the pressure of the lead gas by a predetermined pressure difference; a control valve for regulating the volume flow of the follower gas; the control / regulation unit configured to determine the setpoint for the volume flow of the follower gas depending on the proportion of the follower gas in the fuel gas mixture;a combustion air line which is connected to a fan and the gas burner, wherein the volume flow of the combustion air is adjustable, wherein the control / regulation unit is arranged to determine the setpoint value of the volume flow as a function of a predetermined combustion air ratio, ie the air ratio λ (lambda) and the predetermined proportions of the combustion gases in the combustion gas mixture,

[0043] A preferred embodiment is characterized in that the first fuel gas line and the further fuel gas line can be connected to one another by means of a first lockable connecting line and at least one further lockable connecting line, that the fuel gas lines are preferably designed to be lockable and that the control / regulation unit is designed to guide the guide gas downstream of the pressure control unit to the mixing unit and the follow-up gas downstream of the pressure control unit to the control valve.

[0044] Preferably, at least one controllable shut-off valve is arranged in each of the first fuel gas line and the further fuel gas line, wherein the shut-off valves are preferably located between the connection points of the connecting lines on the fuel gas lines. The connecting lines also have shut-off valves. Preferably, the control and regulation unit is configured to control the shut-off valves such that the guide gas is directed downstream of the pressure control unit to the mixing unit and the follow-up gas is directed downstream of the pressure control unit, optionally through the connecting lines, to the control valve.

[0045] Advantageously, the control / regulation unit is configured to shut off the fuel gas lines and / or the connecting lines if the volume flow of at least one fuel gas is below a predetermined minimum value or above a predetermined maximum value.

[0046] The control / regulation unit causes all shut-off valves to close when the volume flow of at least one fuel gas is below a specified minimum value or above a specified maximum value.

[0047] According to the invention, each pressure control unit comprises a mechanical pressure control device having a diaphragm dividing a chamber into a first and a second space, wherein the first space has a setpoint spring.

[0048] An essential development of the device according to the invention is that the first chamber of the pressure regulator has an opening to which a line is connected in order to guide a non-combustible gas, preferably nitrogen, into the first chamber in such a way that a zero point shift of the force of the setpoint spring is effected.

[0049] Preferably, at least one flow meter is arranged in each fuel gas line for measuring the volume flow of each fuel gas, wherein the measured values ​​can be fed to a ratio control unit for generating a control signal for the control valve in order to keep a predetermined volumetric mixing ratio of the fuel gases constant.

[0050] Advantageously, the volume flow of the combustion air is controlled by means of a speed-adjustable fan or a control flap.

[0051] Within the scope of the invention, the features explained above can also be used in other combinations or on their own. Further details and advantages of the subject matter of the invention will become apparent from the following description in conjunction with the drawing, which describes a preferred embodiment of the invention. The invention is not intended to be limited by the embodiment shown.

[0052] The drawing shows Figure 1 a schematically illustrated system for operating at least one gas burner with two fuel gases, wherein the first fuel gas has the largest proportion of the fuel gas mixture; Figure 2 a schematically illustrated system for operating at least one gas burner with three fuel gases, wherein the first fuel gas has the largest proportion of the fuel gas mixture; Figure 3 a schematically illustrated system for operating at least one gas burner with three fuel gases, wherein the second fuel gas has the largest proportion of the fuel gas mixture; Figure 4 a schematically illustrated system for operating at least one gas burner with three fuel gases, wherein the third fuel gas has the largest proportion of the fuel gas mixture.

[0053] Figure 1shows a schematic system for operating a gas burner for industrial purposes with two fuel gases. The gas burner is used to heat an industrial furnace (not shown), for example, for the heat treatment of steel products.

[0054] The gas burner operates at a load or power level. A gas burner also refers to a group or groups of gas burners. Temperature control of the industrial furnace is achieved by switching individual burners of the burner groups on and off.

[0055] A first fuel gas line 1a for a first fuel gas under increased pressure, here natural gas, leads from a first fuel gas source 2a, in the form of a connection to the public natural gas network, to a mixing unit 3. A further fuel gas line 1b for a further fuel gas under increased pressure, here hydrogen, leads from a second fuel gas source 2b, e.g., a tank, also to the mixing unit 3, in which a fuel gas mixture is generated from the two fuel gases. A fuel gas mixture line 4 leads from the mixing unit 3 to a gas burner 5. The fuel gas mixture is supplied to the gas burner 5 when it is switched on or during phases in which the gas burner is switched on.

[0056] The proportions of the two fuel gases in the fuel gas mixture are specified.

[0057] Depending on the available quantities of hydrogen, hydrogen should replace as much natural gas as possible. The proportion of hydrogen in the fuel gas mixture can be varied as desired.

[0058] A fuel gas mixture line 4 leads from the mixing unit 3 to a gas burner 5. The fuel gas mixture line opens into a combustion chamber, not shown, of the gas burner 5. The fuel gas mixture line 4 can also lead to a group of gas burners or several groups of gas burners and supply them with the fuel gas mixture.

[0059] A control / regulation unit 6, for example a programmable logic controller, has several functional components, at least the components 6a to 6c. The transmission of control / regulation signals is carried out in Figure 1represented by dashed lines. Component 6a of control / regulation unit 6 is configured to store the specified proportions of the combustion gases in the combustion gas mixture and the specified power of the at least one gas burner. Component 6b is configured to determine, from the proportions of the combustion gases in the combustion gas mixture, the combustion gas with the largest proportion in the combustion gas mixture as the lead gas and the at least one additional combustion gas as the follower gas.

[0060] In the exemplary embodiment, the first fuel gas, which originates from the first fuel gas source 2a, is natural gas. Natural gas, at 70 vol.%, is the lead gas. The second fuel gas from the second fuel gas source 2b, in this case hydrogen, is the follower gas at 30 vol.

[0061] A pressure control unit 7a, 7b is arranged in each fuel gas line 1a, 1b.

[0062] The pressure p 2G of the fuel gas mixture determines the flow rate and thus the heating output. When controlling the temperature of an industrial furnace by switching individual gas burners on and off, the required fuel gas flow rate can change very quickly, which is difficult to solve from a control perspective.

[0063] Within the scope of the invention, each pressure control unit 7a, 7b therefore has a mechanical pressure control device 8a, 8b known per se, because mechanical pressure control devices have a low inertia and therefore very good dynamics.

[0064] Each pressure regulator 8a, 8b has a diaphragm (not shown) that divides a chamber into a first and a second space. The first space has a setpoint spring and is connected to the atmosphere via an opening, preferably a known breathing opening.

[0065] A line (not shown) is connected to the opening, by means of which a non-flammable gas, in this case nitrogen, is introduced into the first chamber in order to cause a zero point shift of the force of the setpoint spring.

[0066] The flow QG of a fuel gas mixture through a heating system with at least one gas burner is defined by Q G = B G ∗ Δ p G ρ mix ρ mix = φ H 2 ∗ ρ H 2 + φ NG ∗ ρ NG Δp G = p 2 G

[0067] This is QG the flow in m3 / h at 0°C and 1,013 mbar abs.; BG a fixed flow factor of the heating system; D pG the differential pressure of the fuel gas mixture across the gas burner in mbar; p 2 G the pressure of the fuel gas mixture in front of the gas burner in mbar; ρ mix the density of the fuel gas mixture in kg / m 3< ; ρ H 2 the density of hydrogen kg / m 3< ; ρ NG the density of natural gas in kg / m 3< ; φ NG Volume fraction of natural gas; φ H 2 Volume fraction of hydrogen;

[0068] When using multiple gas burners, the boundary condition is that each gas burner has the same pressure loss at the same output.

[0069] The pressure of the guide gas is regulated by the pressure control unit 7a. Component 6b of the control / regulation unit 6 is configured to specify the setpoint p 2G of the pressure of the guide gas as a function of the desired heating output for pressure control. Pressure gauges 9a, 9b are arranged in each fuel gas line 1a, 1b downstream of the pressure regulators 8a, 8b. The measured values ​​of the pressure gauge 9a are fed to the pressure control unit 7a to regulate the pressure of the guide gas.

[0070] The output of the gas burner remains constant regardless of the proportions of the two fuel gases in the fuel gas mixture.

[0071] The pressure of the follow-up gas is also controlled, whereby the setpoint value of the pressure of the follow-up gas is increased by a predetermined pressure difference compared to the setpoint value p 2G of the pressure of the guide gas by means of the pressure control unit 7b.

[0072] When controlling the pressure of the follower gas, the specified pressure difference between the setpoint p 2G of the pressure of the guide gas and the setpoint of the pressure of the follower gas is between 25 mbar and 500 mbar.

[0073] One of the two fuel gas lines 1a, 1b, namely the fuel gas line 1b, has a control valve 11 for controlling the volume flow of the follow-up gas, wherein the control / regulation unit 6 is configured to determine the setpoint value of the volume flow of the follow-up gas as a function of the proportion of the follow-up gas in the fuel gas mixture.

[0074] Downstream of the pressure gauges 9a, 9b, a flow gauge 10a, 10b is arranged in each fuel gas line 1a, 1b.

[0075] The measured values ​​from the flow meters 10a, 10b are fed to a ratio control unit 12. The measured values ​​generate a signal for adjusting the control valve 11 to maintain a constant volumetric mixing ratio. The volumetric proportions of the follower gas in the fuel gas mixture are kept constant by the control valve.

[0076] The volume fraction of the follower gas, here hydrogen, is given by: ρ H 2 = Q H 2 Q H 2 + Q NG

[0077] The heat load or burner output is the heat content of a fuel gas, related to the lower calorific value, which can be supplied to a gas burner per time interval.

[0078] Compared to natural gas, hydrogen has a lower calorific value per volume. This means that the volume flow of hydrogen must be approximately 3.4 times greater than that of natural gas to achieve comparable burner performance. If the proportion of hydrogen in the gas mixture changes, the volume flows must be adjusted accordingly to ensure constant burner performance.

[0079] The first fuel gas line 1a and the further fuel gas line 1b are connected to each other by means of a first lockable connecting line 13a and a further lockable connecting line 13b.

[0080] Controllable shut-off valves 14a, 14b are located in the first fuel gas line 1a and the second fuel gas line 1b. The connecting lines each have a controllable shut-off valve 15a, 15b. The connecting line 13a is connected to the first fuel gas line at the first connection point 16a and to the second fuel gas line 1b at the first connection point 16b. The connecting line 13b is connected to the first fuel gas line 1a and the second fuel gas line 1b at second connection points 17a and 17b. The shut-off valve 14a in the fuel gas line 1a is located between the first connection point 16a and the second connection point 17a. The shut-off valve 14b in the fuel gas line 1b is arranged between the first connection point 16b and the second connection point 17b in the fuel gas line 1b. The component 6c of the control / regulation unit 6 is configured to control the shut-off valves so that the follow-up gas is directed to the control valve 11.

[0081] In the embodiment according to Figure 1 The fuel gas from fuel gas source 2a is the lead gas. The fuel gas from the second fuel gas source 2b is the follower gas. The flow paths of the lead gas and the follower gas are explained below.

[0082] The guide gas from the fuel gas source 2a flows through the fuel gas line 1a downstream of the pressure control unit 7a or after the pressure regulator 8a through the open shut-off valve 14a to the mixing unit 3. The follow-up gas from the fuel gas source 2b flows through the fuel gas line 1b downstream of the pressure control unit 7b through the open shut-off valve 14b through the control valve 11 to the mixing unit 3.

[0083] In module 6b of control / regulation unit 6, the minimum and maximum values ​​of the volume flow rates of the fuel gases are calculated and specified. Module 6c of control / regulation unit 6 is further configured to close the shut-off valves 14a, 14b in the fuel gas lines 1a and 1b and the shut-off valves 15a, 15b in the connecting lines 13a, 13b when the volume flow rate of the first fuel gas and / or the volume flow rate of the additional fuel gas is / are below the minimum or above the maximum volume flow rate.

[0084] A combustion air line 18 is connected on the one hand to a fan 19 and on the other hand to the gas burner 5. The volume flow of the combustion air is regulated, with the control / regulation unit 6 being configured to determine the setpoint value of the air volume flow as a function of a predetermined combustion air ratio, ie, the air ratio λ and the predetermined proportions of the combustion gases in the combustion gas mixture.

[0085] The combustion air flow rate is controlled by regulating the combustion air pressure in such a way that a fuel gas / combustion air mixture with a predetermined target air ratio λ is provided to the gas burner 5. This is achieved by controlling the speed of the fan 19 using a frequency converter (not shown). Alternatively, a control valve can be used to regulate the combustion air pressure.

[0086] The proportions of natural gas and hydrogen in the fuel gas mixture can be varied as desired, allowing natural gas to be replaced with hydrogen in variable proportions. This allows hydrogen to be used simply and flexibly to generate heat for industrial purposes.

[0087] The Figures 2 to 4each show a schematically illustrated system for operating at least one gas burner with three fuel gases. The components of the system for the fuel gas from the first fuel gas source 2a and the fuel gas from the second fuel gas source 2b correspond Figure 1 . The components in the fuel gas line 1c for supplying a further fuel gas from a third natural gas source to the mixing unit 3 correspond to the components in the fuel gas line 1b in Figure 1 .

[0088] The Figures 2 to 4 serve to illustrate the flow paths of the guide gas and the follower gases. For the sake of clarity, not all components are shown in the Figures 2 to 4 with reference numbers. Please refer to the description of Figure 1 which describes all components.

[0089] In the examples according to Figures 2 to 4The fuel gas from the first fuel gas source 2a is natural gas. The fuel gas from the second fuel gas source 2b is hydrogen. The third fuel gas, which comes from the fuel gas source 2c, is propane in the example.

[0090] For all Figures 2 to 4 The shut-off valves shown in black are open for the respective fuel gas, and the shut-off valves shown in empty are closed. The pipe sections through which no fuel gas flows are shown by dotted lines.

[0091] In the embodiment according to Figure 2 The fuel gas from the first fuel gas source 2a accounts for the largest proportion of the fuel gas mixture and was designated as the lead gas. The fuel gases from the second fuel gas source 2b and the third fuel gas source 2c were designated as follower gases. The flow paths of the lead gas and the follower gases are explained below.

[0092] In Figure 2The guide gas from the fuel gas source 2a flows through the fuel gas line 1a downstream of the pressure control unit 7a or behind the pressure regulator 8a through the open shut-off valve 14a to the mixing unit 3, with the shut-off valves 15a and 15d closed. The follower gas from the second fuel gas source 2b flows through the fuel gas line 1b downstream of the pressure control unit 7b or behind the pressure regulator 8b through the open shut-off valve 14b to the control valve 11 and the mixing unit 3. The follower gas from the third fuel gas source 2c flows through the fuel gas line 1c through the open shut-off valve 14c to the control valve 11' and to the mixing unit 3. The shut-off valve 15c is closed. The fuel gas mixture from the mixing unit 3 is fed to the gas burner 5.

[0093] In the embodiment according to Figure 3The second fuel gas from fuel gas source 2b accounts for the largest proportion of the fuel gas mixture and was designated as the lead gas. The fuel gases from fuel gas sources 2a and 2c were designated as follower gases.

[0094] At Figure 3 the guide gas flows from the fuel gas source 2b through the fuel gas line 1b downstream of the pressure control unit 7b through the open shut-off valve 15b to the mixing unit 3. The shut-off valve 14b is closed.

[0095] The follow-up gas from the fuel gas source 2a flows downstream of the pressure regulator 8a through the open shut-off valve 15a and through the control valve 11 to the mixing unit 3. The shut-off valves 14a and 15d are closed. The follow-up gas from the fuel gas source 2c flows through the fuel gas line 1c downstream of the pressure regulator 7c or behind the pressure regulator 8c through the open shut-off valve 14c and through the control valve 11' to the mixing unit 3. The shut-off valve 15c is closed. The fuel gas mixture from the mixing unit 3 is fed to the gas burner 5.

[0096] At Figure 4 The third fuel gas from fuel gas source 2c constitutes the largest proportion of the fuel gas mixture and was designated as the lead gas. The fuel gases from fuel gas sources 2a and 2b were designated as the follower gas.

[0097] The guide gas from the fuel gas source 2c flows through the fuel gas line 1c downstream of the pressure control unit 7c or behind the pressure control device 8c through the open shut-off valve 15c to the mixing unit 3. The shut-off valve 14c is closed.

[0098] The follow-up gas from the fuel gas source 2a flows downstream of the pressure regulator 8a through the open shut-off valve 15d and through the control valve 11' to the mixing unit 3. The shut-off valves 14a and 15a are closed. The follow-up gas from the fuel gas source 2b flows through the fuel gas line 1b downstream of the pressure regulator 8b through the open shut-off valve 14b and through the control valve 11 to the mixing unit 3. The shut-off valve 15b is closed. The fuel gas mixture from the mixing unit 3 is fed to the gas burner 5.

[0099] Modifications are readily possible within the scope of the invention. For safety reasons, two flow meters can be provided in each fuel gas line. A fuel gas mixture can also be used as the fuel gas.

[0100] Finally, it is noted that the term "comprising" does not exclude any elements, that the reference signs are not limiting, and that the word "a" or "an" includes a plurality. List of reference symbols

[0101] 1a, 1b, 1c Fuel gas line 2a First fuel gas source 2b Second fuel gas source 2c Third fuel gas source 3 Mixing unit 4 Fuel gas mixture line 5 Gas burner 6 Control / regulation unit 6a, 6b Modules of the control / regulation unit 6 7a, 7b, 7c Pressure control unit 8a, 8b, 8b Pressure regulator 9a, 9b Pressure gauges 10a, 10b, 10c Pressure flow meter 11, 11 Control valve 12 Ratio control unit 13a, 13b Connecting lines 14a, 14b, 14c Shut-off valves in fuel gas lines 15a, 15b, 15c, 15d Shut-off valves in connecting lines 16a, 16b, 16c First connection point connecting line / fuel gas line 17a, 17bSecond connection point connecting line / fuel gas line 18Combustion air line 19Blower

Claims

1. A method for operating at least one gas burner (5) for industrial use with at least two fuel gases, which are supplied by means of a first fuel gas line (1a) and at least one further fuel gas line (1b, 2c) to a mixing unit (3) for producing a fuel gas mixture, which is made available to the gas burner (5), wherein the proportions of the fuel gases in the fuel gas mixture are predetermined, with at least the following method steps: - determining the fuel gas with the largest proportion as the guide gas and the at least one further fuel gas as the follower gas by means of a control / regulation unit (6), - regulating the pressure of the guide gas by means of a pressure regulating unit (7a, 7b, 7c), wherein the setpoint value (p 2G) of the pressure of the guide gas is specified as a function of the desired heating power by means of the control / regulation unit (6), - regulating the pressure of the follower gas by means of the pressure control unit (7a, 7b, 7c), wherein the setpoint value of the pressure of the follower gas is higher than the setpoint value (p 2G ) the pressure of the guide gas, - guiding the follow-up gas to a control valve (11, 11') and controlling the volume flow, wherein the setpoint value of the volume flow of the follow-up gas is determined as a function of the proportion of the follow-up gas in the fuel gas mixture, - supplying combustion air to the gas burner (5) by means of a fan (19), wherein the volume flow of the combustion air is controlled and wherein the setpoint value of the volume flow is determined as a function of a predetermined combustion air ratio (λ) and the proportions of the fuel gases in the fuel gas mixture.

2. Method according to claim 1, characterized in thatthe guide gas is conducted downstream of the pressure control unit (7a, 7b) to the mixing unit (3) and the follower gas is conducted downstream of the pressure control unit (7a, 7b) to the control valve (11, 11') by means of a first lockable connecting line (13a) and at least one further lockable connecting line (13b) which connect the first and fuel gas lines (1a) to the further fuel gas lines (1b) with one another, and that the fuel gas lines (1a, 1b) are preferably designed to be lockable.

3. Method according to claim 1 or 2, characterized in that the supply of the fuel gases to the mixing unit (3) is interrupted if the volume flow of at least one fuel gas is below a predetermined minimum value or above a predetermined maximum value.

4. Method according to at least one of the preceding claims, characterized in thatthe pressure control unit (7a, 7b) comprises a mechanical pressure control device (8a, 8b) which has a diaphragm which divides a chamber into a first and a second space, and in that the first space has a setpoint spring which acts on the diaphragm.

5. Method according to claim 4, characterized in that a zero point shift of the force of the setpoint spring is effected by introducing a non-combustible gas, preferably nitrogen, into the first space through an opening in the first space of the chamber of the pressure regulator (8a, 8b).

6. Method according to at least one of the preceding claims, characterized in that When controlling the pressure of the follower gas, the specified pressure difference between the setpoint pressure (p 2G ) of the guide gas and the setpoint pressure of the follower gas is between 25mbar and 500mbar.

7. Method according to at least one of the preceding claims, characterized in thatTo control the volume flow of the follower gas, the volume flows of the guide gas and the follower gas are measured with at least one flow meter (10a, 10b) each and the measured values ​​are fed to a ratio control unit (12) for generating a control signal for the control valve (11, 11') in order to keep a predetermined volumetric mixing ratio constant.

8. Method according to at least one of the preceding claims, characterized in that To regulate the volume flow of the combustion air, the speed of the fan (19) is regulated or a control flap is used.

9. System for operating at least one gas burner (5) for industrial use with at least two fuel gases, with a first fuel gas line (1a) and at least one further fuel gas line (1b, 1c) for supplying the fuel gases to a mixing unit (3) for generating a fuel gas mixture, which is provided to the gas burner (5) by means of a fuel gas mixture line (4), wherein the proportions of the fuel gases in the fuel gas mixture are predetermined, at least comprising: - a control / regulation unit (6) which is designed to determine, from the predetermined proportions of the fuel gas in the fuel gas mixture, the fuel gas with the largest proportion in the fuel gas mixture as the guide gas and the further fuel gas as the follower gas, - a pressure control unit (7a, 7b, 7c) in each fuel gas line (1a, 1b, 1c), wherein each pressure control unit (7a, 7b, 7c) is selectively designed to regulate the pressure (p 2G) of the guide gas or for regulating the at least one follower gas, wherein the control / regulation unit (6) is arranged to determine a setpoint (p 2G ) of the pressure of the guide gas depending on the desired heating power and to specify a setpoint value of the pressure of the follower gas which is higher than the setpoint value (p 2G) the pressure of the guide gas, - a control valve (11, 11') for controlling the volume flow of the follow-up gas, wherein the control / regulation unit (6) is set up to determine the target value of the volume flow of the follow-up gas as a function of the proportion of the follow-up gas in the fuel gas mixture, - a combustion air line (18) which is connected to a fan (19) and the gas burner (5), wherein the volume flow of the combustion air is controllable, wherein the control / regulation unit (6) is set up to determine the target value of the volume flow as a function of a predetermined combustion air ratio and the predetermined proportions of the fuel gases in the fuel gas mixture.

10. System according to claim 9, characterized in thatthe first fuel gas line (1a) and the further fuel gas line (1b, 1c) can be connected to one another by means of a first lockable connecting line (13a) and at least one further lockable connecting line (13b), that the fuel gas lines (1a, 1b, 1c) are preferably designed to be lockable and that the control / regulation unit (6) is set up to guide the guide gas downstream of the pressure control unit (7a, 7b) to the mixing unit (3) and the follow-up gas downstream of the pressure control unit (7a, 7b, 7c) to the control valve (11, 11').

11. System according to claim 10, characterized in that the control / regulation unit (6) is designed to shut off the fuel gas lines (1a, 1b, 1c) and / or the connecting lines (13a, 13b) if the volume flow of at least one fuel gas is below a predetermined minimum value or above a predetermined maximum value.

12. System according to at least one of the preceding claims 9 to 11, characterized in thateach pressure control unit (7a, 7b, 7c) comprises a mechanical pressure control device (8a, 8b, 8c) which has a diaphragm which divides a chamber into a first and a second space and in that the first space has a setpoint spring.

13. System according to claim 12, characterized in that the first chamber of the pressure regulator (8a, 8b, 8c) has an opening to which a line is connected in order to conduct a non-combustible gas, preferably nitrogen, into the first chamber in such a way that a zero point shift of the force of the setpoint spring is effected.

14. System according to at least one of the preceding claims 9 to 13, characterized in thatin each fuel gas line (1a, 1b, 1c) at least one flow meter (10a, 10b, 10b) is arranged for measuring the volume flow of each fuel gas and that the measured values ​​can be fed to a ratio control unit (12) for generating an actuating signal for the control valve (11, 11') in order to keep a predetermined volumetric mixing ratio of the fuel gases constant.

15. System according to at least one of the preceding claims 9 to 14, characterized by a speed-adjustable fan (19) or a control flap for regulating the volume flow of the combustion air.

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